1. Field of the Invention
The present invention relates to a humidity-sensing component composition which detects relative humidity as a change in the value of the electrical resistance.
2. Description of the Prior Art
Conventionally, materials known as humidity-sensing component compositions are:
(1) Materials using electrolytic quality salts such as lithium chloride;
(2) Materials utilizing organic polymer films such as polyamide or polyethylene films;
(3) Materials using metallic semiconductors such as selenium or germanium; and
(4) Materials utilizing sintered bodies of metallic oxides such as titanium oxide, aluminium oxide, or stannic oxide.
Among these, the materials using sintered bodies of metallic oxides have the merit of being more stable chemically and physically than other humidity-sensing component compositions such as organic polymer films, and these can be said to be effective as humidity-sensing component compositions.
However, these sintered bodies of metallic oxides usually have the following types of drawbacks:
(1) The characteristic resistance value is high, and is not in the practical resistance value range. In regions of low humidity especially, the resistance of the humidity-sensing component composition abruptly becomes high, so the measurement of humidity in regions of low humidity is difficult.
(2) Dependence on temperature in the humidity-sensing characteristics is large, so temperature compensation is necessary.
(3) Hysteresis in the humidity-sensing characteristics is encountered when moisture is absorbed and released.
(4) Resistance to thermal shock is low, and the humidity-sensing characteristics deteriorate.
(5) Products of hydration are absorbed on and foul the surface of sintered bodies of metallic oxides so that the humidity-sensing characteristics deteriorate, making periodic heat cleaning necessary.
For these reasons, the development of a humidity-sensing component composition with high reliability has been greatly desired.